The present invention relates to a transmission apparatus for video information, a transmission system for video information and a transmission method for video information.
The application field of computers is growing wider in recent years. Under these conditions, a computer which is divided into a part (referred to as xe2x80x9cfirst terminal apparatusxe2x80x9d) which includes a CPU (central processing unit) or the like, and a part (referred to as xe2x80x9csecond terminal apparatusxe2x80x9d) which includes a display part for the video (or a display part and an input part) is in demand by the market.
FIG. 10 is a conceptual diagram of a computer which has a first terminal apparatus and a second terminal apparatus.
In FIG. 10 the first terminal apparatus which includes a CPU is denoted as 1001, the second terminal apparatus which includes a display part and a pen input part is denoted as 1002, a conventional PC (abbreviation of personal computer which has a CPU and a display part) is denoted as 1003, a docking station is denoted as 1004, a keyboard is denoted as 1005 and a display part is denoted as 1006. The first terminal apparatus 1001 has a CPU 1011 and a wireless communication part 1012. The second terminal apparatus 1002 has a display and pen input part 1021 and a wireless communication part 1023. The user can input an instruction into a computer by touching the display and pen input part 1021 with a pen 1022.
Video information generated in the CPU 1011 of the first terminal apparatus 1001 is transmitted from the wireless communication part 1012. The wireless communication part 1023 of the second terminal apparatus 1002 receives the video information and transmits it to the display and pen input part 1021. The display and pen input part 1021 displays the inputted video information.
When the user inputs, with a pen 1022, an instruction to the computer by means of the display and pen input part 1021 of the second terminal apparatus, this instruction information is transmitted from the wireless communication part 1023. This instruction information is inputted to the wireless communication part 1012 of the first terminal apparatus 1001 and is transmitted to the CPU 1011. The CPU 1011 inputs the instruction information and processes information according to the instruction information.
The user generally utilizes only the first terminal apparatus 1001 and the second terminal apparatus 1002. The user can move about freely while carrying the second terminal apparatus 1002, which is light and has no connection lines.
The user can also construct and utilize a computer system comprising the first terminal apparatus 1001, the docking station 1004, the keyboard 1005 and the display part 1006 by connecting the docking station 1004 to the first terminal apparatus 1001 and by connecting the keyboard 1005 and the display part 1006 to the docking station 1004.
The conventional PC 1003 can incorporate a wireless communication part 1031, which is an option. The video information generated by the CPU of the PC 1003 is transmitted from the wireless communication part 1031. The wireless communication part 1023 of the second terminal apparatus 1002 receives the video information and transmits it to the display and pen input part 1021. The display and pen input part 1021 displays the inputted video information.
When the user inputs, with the pen 1022, an instruction to the computer by means of the display and pen input part 1021 of the second terminal apparatus, this instruction information is transmitted from the wireless communication part 1023. The wireless communication part 1031, which is incorporated in the conventional PC 1003, inputs this instruction information and transmits it to the CPU. The CPU of the conventional PC 1003 inputs the instruction information and processes information according to the instruction information.
In this manner, the user can utilize a conventional PC as the first terminal apparatus 1001.
FIG. 11 is a block diagram of a conventional computer which has a first terminal apparatus and a second terminal apparatus (primarily shows a transmission apparatus for video information and a transmission system for video information included in the computer). The conventional computer of FIG. 11 includes a transmission apparatus for video information which transmits video information from the first terminal apparatus to the second terminal apparatus.
In FIG. 11, the first terminal apparatus is denoted as 1101, the second terminal apparatus is denoted as 1102, a display (display part) is denoted as 1003 and a wire for connecting the first terminal apparatus 1101 with the second terminal apparatus 1102 is denoted as 1104.
The first terminal apparatus 1101 has a CPU 1111, a video graphics control part 1113, an LCD driving part 1115 (liquid crystal display driving part), a liquid crystal display 1116 and a communication board 1114. The description of a ROM, a RAM or the like, which do not directly relate to the present invention, is omitted though they are indispensable to a computer.
The CPU 1111, the video graphics control part 1113 and the communication board 1114 are connected to each other via a PCI bus 1112.
The video graphics control part 1113 has a CPU 1121, an input/output part 1122, a RAM 1123, a VRAM 1124, a write in/read out address register 1125, a read out address register 1126, a clock generator 1127 and a parallel/serial conversion part 1128.
The CPU 1121, the input/output part 1122, the RAM 1123, the VRAM 1124, the write in/read out address register 1125 and the like are connected to each other via an internal bus 1129.
The CPU 1111 transmits an instruction described in a software language (for example, DirectX (registered trademark of Microsoft Corporation)) for changing the video to the video graphics control part 1113 and the communication board 1114 via the PCI bus 1112.
The input/output part 1122 of the video graphics control part 1113 transmits the inputted instruction described in a software language for changing the video to the CPU 1121 via the internal bus 1129.
The CPU 1121 converts an instruction described in a software language (program arranged on an Application Programming Interface of OS of the computer) for changing the video into level information (for example, information concerning the value to which the value of any address of the VRAM is changed) of each pixel at a hardware level by utilizing a video information decoder 1141. The RAM 1123 is a scratch region at the time when level information of each pixel is generated by utilizing the video information decoder 1141. The VRAM 1124 is a dual port RAM for video display which has a port which can write in or read out by randomly accessing an arbitrary address (an address is designated by the write in/read out address register 1125) and a port which can read out data of each address at a high rate and in a constant order (an address is designated by the read out address register 1126). The level information of each pixel (level information of each of the sub-pixels RGB), attribute data and the like are stored in the VRAM 1124.
The CPU 1121 and the like set an address in the write in/read out address register 1125. Information is written in to this address through the internal bus 1129 and information is read out from this address through the internal bus 1129.
The clock generator 1127 sets a read out address register 1126. The set value of the address register 1126 is generally incremented at an extremely high rate. The information of the address designated by the address register 1126 is read out and forwarded to the parallel/serial conversion part 1128. The parallel/serial conversion part 1128 converts the inputted information of each address (level information of each pixel) into serial data, which are outputted.
The output signal of the parallel/serial conversion part 1128 is transmitted to the LCD driving part 1115 and is converted into an LCD (liquid crystal display) driving signal. The LCD driving part 1115 drives the liquid crystal display 1116. The liquid crystal display 1116 displays the video.
In addition, the output signal of the parallel/serial conversion part 1128 is transmitted to the external display 1103. The display 1103 displays the video.
The communication board 1114 receives an instruction which is described in a software language for changing the video (outputted by the CPU 1111) and which is transmitted through the PCI bus 1112. The communication board 1114 transmits the instruction described in a software language for changing the video to the second terminal apparatus 1102 through connection via the wire 1104.
The communication board 1131 of the second terminal apparatus 1102 transmits the received instruction described in a software language for changing the video to a video graphics control part 1132. The video graphics control parts 1132 and 1113 have the same configuration. The video graphics control part 1132 generates display data of each pixel based on the instruction described in a software language for changing the video, and outputs them. A display 1133 displays the video by driving each pixel in accordance with the display data.
FIG. 12 schematically shows the hierarchical structure of a conventional computer which has the first terminal apparatus 1101 and the second terminal apparatus 1102. The first terminal apparatus 1101 has a software layer 1203 which is the upper layer and a hardware layer 1204 which is the lower layer. The software layer 1203 has an application program 1211, an OS (operating system) 1212, and device drivers 1213 and 1214. The hardware layer 1204 has the video graphics control part 1113 (including the VRAM 1124), the display 1103 and the communication board 1114. The application program 1211 operates on the OS 1212 while the device drivers 1213 and 1214 depend on the OS 1212.
The video graphics control part 1113 is controlled by the device driver 1213 while the communication board 1114 is controlled by the device driver 1214.
The second terminal apparatus 1102 has a software layer 1205, which is upper layer, and a hardware layer 1206, which is the lower layer. The software layer 1205 has device drivers 1215, 1216 and 1217 which depend on the OS 1212 stored in the first terminal apparatus. The hardware layer 1206 has the communication board 1131, a pen input part 1231, the video graphics control part 1132 (including a VRAM 1232) and the display 1133. The device drivers 1215, 1216 and 1217 communicate with the OS 1212 through the communication boards 1114 and 1131.
The video graphics control part 1132 is controlled by the device driver 1217, the pen input part 1231 is controlled by the device driver 1216 and the communication board 1131 is controlled by the device driver 1215.
The user can input video information (arbitrary information concerning video drawing) described in a software language by using an application program 1211 (for example, DirectX) located on the OS 1212. This information for changing the video is transmitted to the OS 1212 (OS 1212 operates on the CPU 1111) through the API 1221 (Application Programming Interface, which is included in OS). The OS 1212 transmits this video information to the device driver 1213. The device driver 1213 generates level information of each pixel based on this video information and stores the level information of each pixel in the VRAM 1124. The level information of each pixel stored in the VRAM 1124 is read out by a hardware circuit (clock generation circuit 1127 or the like) and displayed on the display 1103.
In addition, the OS 1212 transmits the inputted video information to the device driver 1217 of the second terminal apparatus through the communication boards 1114 and 1131. The device driver 1217 generates level information of each pixel based on this video information and stores the level information of each pixel in the VRAM 1232. The level information of each pixel stored in the VRAM 1232 is read out by a hardware circuit (clock generation circuit or the like) and is displayed on the display 1133.
The user can input an instruction (assumed to be a video change instruction) to the computer from the pen input part 1231 of the hardware layer 1206. The video change instruction inputted by the user is converted into information (video change instruction information) in the software by the device driver 1216. The video change instruction information is transmitted to the OS 1212 through the communication boards 1131 and 1114. The OS 1212 transmits this video change instruction information to the application program 1211 through the API 1221. The application program 1211 generates new video information according to this video change instruction information.
In the following, by carrying out the above described process, the video graphics control parts 1113 and 1132 output level information of each pixel which are newly generated, respectively.
In the conventional computer which has the first terminal apparatus and the second terminal apparatus, however, the exchange of information between the first terminal apparatus and the second terminal apparatus is carried out by a video change instruction described in a software language. Therefore, transmission and reception of data cannot carried out between the first terminal apparatus and the second terminal apparatus wherein different OSs are installed.
For example, in FIG. 12, in the case that the device drivers 1215, 1216 and 1217 installed in the second terminal apparatus 1102 depend on an OS which is different from the OS 1212 installed in the first terminal apparatus 1101, the device driver 1217 does not respond to the inputted video information even when the video information is transmitted from the first terminal apparatus to the second terminal apparatus.
In particular, the user who has a plurality of first terminal apparatus in which different OSs are installed must precisely select the combination between the first terminal apparatus wherein the first OS is installed and the second terminal apparatus which depends on the first OS as well as the combination between the first terminal apparatus wherein the second OS is installed and the second terminal apparatus which depends on the second OS for use and, therefore, mistakes can easily occur. For example, in the case that that the user goes out carrying the first terminal apparatus wherein the first OS is installed and the second terminal apparatus which depends on the second OS those apparatus, they cannot be used after all. Therefore, the user who has a plurality of first terminal apparatus in which different OSs are installed requires a data forwarding system between the first terminal apparatus and the second terminal apparatus which is independent of differences in OSs.
There is also the idea of transmitting the output signal of the parallel/serial conversion part 1128 to the second terminal apparatus 1102 without change. However, in the case, for example, that a full color display of 8 bits each for RGB is shown on the screen of UXGA (1600xc3x971200 pixels), the output signal of the parallel/serial conversion part 1128 exceeds 46 Mbps. It is extremely difficult to transmit data at such a high rate in a wireless manner.
The present invention has the purpose of providing a transmission apparatus for video information, a transmission system for video information and a transmission method for video information which make possible a wireless transmission of video information at a low rate regardless of differences in OSs.
The present invention has the following configurations in order to solve the above described problem.
The invention according to claim 1 is a transmission apparatus for video information characterized by having:
an input part for inputting video information transmitted by a central processing unit; a level information generation part for generating level information of each pixel on a screen based on, at least, said video information; a memory part for storing level information of each pixel of the entire region of the screen; a comparison part for comparing level information stored in said memory part with level information outputted by said level information generation part with respect to said pixel associated with said video information and for outputting comparison information; a region extraction part for extracting a region that includes a pixel wherein the level information stored in said memory part and the level information based on said video information are different according to said comparison information; a compression part for compressing the information amount of the level information of each pixel of said extracted region of the screen; and a communication part for transmitting position information of said region of the screen and said compressed level information.
The invention according to claim 2 is a transmission apparatus for video information characterized by having: an input part for inputting video information transmitted by a central processing unit; a level information generation part for generating level information of each pixel on a screen based on, at least, said video information; a memory part for storing level information of each pixel of the entire region of the screen; a comparison part for comparing level information stored in said memory part with level information outputted by said level information generation part with respect to said pixel associated with said video information and for outputting comparison information; a region extraction part for extracting a region that includes a pixel wherein the level information stored in said memory part and the level information based on said video information are different according to said comparison information; an update region level information generation part for generating differential information between the level information stored in said memory part and the level information outputted by said level information generation part with respect to each pixel of said extracted region of the screen; a compression part for compressing the information amount of said differential information; and a communication part for transmitting position information of said region of the screen and said compressed differential information. The invention according to claim 3 is a transmission apparatus for video information according to claim 1 or 2 characterized in that said communication part is a wireless communication part.
The invention according to claim 4 is a transmission apparatus for video information according to claim 1 or 2 further characterized in that: said update region level information generation part outputs level information of each pixel of the entire region of the screen at least once or more for a constant period of time; said compression part compresses the information amount of the level information of said entire region of the screen; and said communication part transmits identification information for identifying said compressed level information of the entire region of the screen from said compressed level information of the region of the screen or said compressed differential information, as well as said compressed level information of the entire region of the screen.
The invention according to claim 5 is a transmission system for video information characterized by having: a first terminal apparatus that includes a central processing unit and a transmission apparatus for video information according to claim 1; and a second terminal apparatus, wherein said second terminal apparatus has: a communication part for receiving said position information of the region of the screen and said compressed level information; an expansion part for expanding said compressed level information and for outputting level information of each pixel of the extracted region of the screen; a memory part for storing level information of each pixel of the entire region of the screen and for storing the level information of each pixel outputted by said expansion part according to said position information of the region of the screen; and a display part for displaying a screen according to level information of each pixel stored in said memory part.
The invention according to claim 6 is a transmission system for video information characterized by having: a first terminal apparatus that includes a central processing unit and a transmission apparatus for video information according to claim 2; and a second terminal apparatus, wherein said second terminal apparatus has: a communication part for receiving said position information of the region of the screen and said compressed differential information; an expansion part for expanding said compressed differential information and for generating differential information of each pixel of the extracted region of the screen; a memory part for storing the level information of each pixel of the entire region of the screen and for storing the level information of each pixel generated by the level information generation part according to position information of said region of the screen; said level information generation part for generating the level information of each pixel based on the differential information of each pixel generated by said expansion part and level information of each pixel stored in said memory part; and a display part for displaying a screen according to the level information of each pixel stored in said memory part.
The invention according to claim 7 is a transmission system for video information according to claim 5 or 6 characterized in that said communication parts of said first terminal apparatus and said second terminal apparatus are wireless communication parts, respectively.
The invention according to claim 8 is a transmission method for video information characterized by having: an input step for inputting video information transmitted by a central processing unit; a level information generation step for generating the level information of each pixel on a screen based on, at least, said video information; a comparison step for comparing level information stored in a memory part with level information generated in said level information generation step in respect to said pixel associated with said video information and for generating comparison information; a region extraction step for extracting a region that includes a pixel wherein the level information stored in said memory part and the level information based on said video information are different according to said comparison information; a compression step for compressing the information amount of the level information of each pixel of said extracted region of the screen; and a communication step for transmitting position information of said region of the screen and said compressed level information.
The invention according to claim 9 is a transmission method for video information characterized by having: an input step for inputting video information transmitted by a central processing unit; a level information generation step for generating level information of each pixel on the screen based on, at least, said video information; a comparison step for comparing the level information stored in a memory part with the level information generated in said level information generation step with respect to said pixel associated with said video information and for generating comparison information; a region extraction step for extracting a region which includes a pixel wherein the level information stored in said memory and the level information based on said video information are different according to said comparison information; an update region level information generation step for generating differential information between the level information stored in said memory part and the level information generated in said level information generation step with respect to each pixel of said extracted region of the screen; a compression step for compressing the information amount of said differential information; and a communication step for transmitting position information of said region of the screen and said compressed differential information.
The invention according to claim 10 is a transmission method for video information according to claim 8 or 9 characterized in that a wireless communication is carried out in said communication step.
The invention according to claim 11 is a transmission method for video information according to claim 8 or 9 characterized by further having: an entire region level information generation step for reading out the level information of each pixel of the entire region of the screen from said memory part with a frequency of, at least, once or more in a constant period of time; an entire region level information compression step for compressing the information amount of the level information of the entire region of the screen; and an entire region level information transmission step for transmitting identification information for identifying said compressed level information of the entire region of the screen from said compressed level information of the region of the screen or said compressed differential information, as well as said compressed level information of the entire region of the screen.
The invention according to claim 12 is a transmission method for video information characterized by having: each step of the transmission method for video information according to claim 8; a communication step for receiving position information of said region of the screen and said compressed level information; an expansion step for expanding said compressed level information and for outputting the level information of each pixel of the extracted region of the screen; a memory step for storing the level information of each pixel generated in the expansion step according to the position information of said region of the screen; and a display step for displaying a screen according to the level information of each pixel stored in said memory part.
The invention according to claim 13 is a transmission method for video information characterized by having: each step of the transmission method for video information according to claim 9; a reception step for receiving position information of said region of the screen and said compressed differential information; an expansion step for expanding said compressed differential information and for generating differential information of each pixel of the extracted region of the screen; a level information generation step for generating the level information of each pixel based on the differential information of each pixel generated in said expansion step and the level information of each pixel stored in the memory part; a memory step for storing the level information of each pixel generated in said level information generation step in said memory part according to the position information of said region of the screen; and a display step for displaying a screen according to the level information of each pixel stored in said memory part.
The invention according to claim 14 is a transmission method for video information according to claim 12 or 13 characterized in that said transmission step and said reception step are carried out by means of a wireless communication.
According to the present invention, all of the video information is not transmitted but, rather, only information of the part where video data have changed is transmitted. In addition, by utilizing differential information of data (difference between previous data and current data), the amount of the transmitted information can be further reduced.
The present invention has the effect that a transmission apparatus for video information, a transmission system for video information and a transmission method for video information that make the transmission (particularly transmission by means of wireless communication) of video information at a low bit rate possible regardless of differences in OSs can be implemented.
Though the new characteristics of the invention are nothing other than what are specifically described in the attached claims, the present invention will be better understood and appreciated, concerning both the configuration and contents, with reference to the detailed description below which is to be understood in conjunction with the drawings, together with other purposes and characteristics.